The h Bar - 2021-05-08

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6:52 AM

If there's a moderator with a bit of spare time around would you be able to do me a favour and delete some chat posts that contain personal data? (Not my personal data - a student who failed to realise that publicly uploading personal data isn't the best move.)

2 hours later…

8:32 AM

Hi folks, I was observing that most books on dynamical billiards are by Russian authors, also most work on them are done by Russians... I was wondering what the reason(non political) could be...

2 hours later…

10:29 AM

This answer on an old question isn't exactly spam, since he does disclose his affiliation. OTOH, it is promoting a personal non-mainstream theory. So should I flag it with a custom flag?

@kbakshi314 Those 2 questions are a bit better than pure Problem Statement Questions, but they're close. At least the OPs made some effort to describe what issues they have. So IMHO, both questions could potentially be adjusted to make them more on-topic by focusing on the OPs' core conceptual problems.

@JohnRennie if you haven't found someone else yet, I could do that now

As I recently said here, one problem with PSQs (Problem Statement Questions) is that we generally don't know why the OP needs help. We don't know what misunderstanding or gap in their knowledge prevents them from doing the homework assignment themself.

@PM2Ring It's definitely not spam by SE's rather strict definition and we usually don't delete answers just for being wrong - I'd just downvote and move on

@ACuriousMind thanks :-)

In this room

The user has posted pictures of themselves, their signature and their fingerprint!!!

And even if another student comes along who's having difficulties with the exact same exercise, it's possible that they have different conceptual difficulties to the original OP. So an answer that helps the first OP may not help the new reader very much. Of course, they'll both get some benefit in seeing a correct way of solving the exercise. ;)

10:40 AM

@JohnRennie I assume I should remove the links to your mirrors of these files as well, or do you just want to take them down?

Yes please, delete them too.

Thanks :-)

@JohnRennie Oh dear. An even worse scenario: they're someone else's details.

@PM2Ring I doubt it actually matters, but it seems sensible to delete them.

@ACuriousMind Well, it's not even wrong. It's pretty difficult to see how it's relevant at all to the OP question, apart from invoking an extra dimension.

@PM2Ring in that case, why not just flag as "not an answer"?

10:45 AM

@JohnRennie I hear that identity theft is a thriving industry. OTOH, you can't steal much from a poor person. But still, it'd be horrible to have your identity compromised, no matter what your socio-economic standing is.

@ACuriousMind Yeah, ok.

worldscientific.com/worldscibooks/10.1142/1908

@PM2Ring well yes, hence my eagerness to get the posts deleted.

Anyone knows how to obtain this book

I tried buying it, but the payment system won't accept my credit card

I tried libgen but they don't seem to have it

It doesn't seem to be available on Amazon

@JohnRennie did you tell this user somewhere else why this was a Bad Idea? I'm not seeing anything in the transcript

They've gone offline, but then next time I speak to them I will mention it.

10:48 AM

@ACuriousMind I was hoping that the author would explain how his post answers the question. But he hasn't responded to my comments, so I'm happy to give him a flag. ;)

@Slereah ...get a better credit card? :P

@ACuriousMind I suspect my credit card isn't the one at fault here

although if you want

you can lend me yours

lol, I don't even have a credit card

I will accept wire transfer

I hope that worldscientific isn't a scam to get my credit card details

ah yes, the old "pretending to be a physics publisher to scam people desparate for rare physics books" trick

10:53 AM

It's exactly because it's such an unlikely event that it works so well

Nobody's expecting it

@Slereah Do they take Bitcoin? :D

They don't even take paypal

I was horrified to learn recently that Bitcoin currently consumes 121.36 terawatt-hours per annum. That's over 4.86 kg * c². I assume most of that energy is being expended in mining. It seems like a shocking waste to me.

it is

It wouldn't be quite so bad if all those calculations were doing something useful, rather than just solving a hash function puzzle.

11:21 AM

@PM2Ring from the miner's viewpoint, it is doing something useful - it's making them richer :P

why not sell drugs if you really want to get money in morally questionable ways

I'm sure making meth has less of a carbon footprint

and more stability

@ACuriousMind Sure. But it's still a really wasteful way of printing money.

I don't disagree - it's just that the miners are just following incentives. I'd lay the blame with the people willing to treat it like money in the first place.

2

Agreed

I guess people have tried to come up with cryptocurrency schemes based on useful computations, eg protein folding, or even finding zeroes of the Riemann zeta function. But they haven't figured out how to do that yet.

11:58 AM

The fundamental problem with the idea of cryptocurrencies is that they're supposed to be decentralized, but regardless of what kind of "proof" method they use they're always vulnerable to become centralized in the hands of the people who have enough resources to acquire the most storage space/computing power/etc.

and realistically in order for them to have purchasing power you always need some sort of exchange willing to couple them to real-world currencies

12:57 PM

hmmm good question

thats certainly the case for the foreseeable future

i wonder if there is some elusive solution to the centralisation problem

@antimony If you find that solution, please let us know. ;)

"All animals are equal, but some animals are more equal than others." - George Orwell, Animal Farm

"Meet the new boss. Same as the old boss." - Peter Townshend, Won't Get Fooled Again

Favourite question title of the day: "Cyphons and the persistent confusion of vacuum as a force".

The Persistent Confusion of Vacuum would be a great album title, eg for a David Gilmour and Robert Fripp collaboration. ;)

1:12 PM

What is meant by decentralized ledger-based blockchain technology?

I tried wikipedia..

But for a layman it is difficult to understand

@PM2Ring cyphon?

@RajorshiKoyal Bitcoin has a FAQ: bitcoin.org/en/faq There's also a Bitcoin stack site: bitcoin.stackexchange.com

@FadedGiant An unusual way of spelling "siphon".

ah

Does anyone here have an idea about this?

@RajorshiKoyal A ledger is just a system for recording financial transactions. A blockchain uses cryptographic techniques to ensure that the records of the transactions cannot be tampered with.

@RajorshiKoyal The ledger isn't stored in a single central place. Anybody is free to store a copy of the ledger on their own computer. And anyone can use the freely available software to verify the validity of the records in the ledger. However, the ledger isn't small, it currently consumes a little over 330 gigabytes.

1:40 PM

But why decentralized please tell this to me.

@PM2Ring

2:08 PM

Is it the case that a redshifted blackbody spectrum is the same as a blackbody spectrum corresponding to a different temperature? I used to “know” this, and I think it’s the explanation for the CMB still being a blackbody spectrum, but sometimes I “know” things that aren’t actually so.

@rob yes, see physics.stackexchange.com/a/354864/50583

@RajorshiKoyal You may find this article helpful: bitcoinmarketjournal.com/decentralized-currency I agree that it's not easy to understand cryptocurrency. And it's not something that can be explained in a few minutes. There's lots of info about it available online, and it's helpful to browse the various FAQs. OTOH, there are articles that have lots of hype and not much useful info, from organisations who just want your money. ;)

@ACuriousMind Thanks!

@rob There's a good WP link posted by Anna V on that page that ACM linked: en.wikipedia.org/wiki/…

@PM2Ring Brilliant. It’s always a relief when something I “know” turns out to be an actual fact.

2:18 PM

In my book it says that cryptocurrency is not backed by any physical asset. What does this mean?

@rob Definitely!

@RajorshiKoyal It used to be (long ago) that money was more or less just a token corresponding to you owning some amount of gold or other assets. You could, in principle, have gone to a bank and demanded that they take your money and give you the corresponding asset.

ok

cryptocurrencies aren't like that - owning a bitcoin doesn't correspond to owning anything in the real world - but then again, most real-world currencies aren't like that either these days

ok but how is that a disadvantage that way?

2:23 PM

@RajorshiKoyal What ACM said. Money backed by a physical asset like gold is called representative money

whether or not it is a disadvantage depends on your economic views :P

ok..

What is meant by extreme volatility..

Like it says extreme volatility makes it prone to gambling..

Please explain this to me :-)

Some people argue that money should be backed by assets since otherwise its value depends only on people's beliefs that it is worth something; others would argue all assessments of value are ultimately just social contracts and fiat money is just more honest about it

What is meant by fiat currency please explain this to me:-)

fiat money is just the opposite of representative money, i.e. money that's not backed by assets

2:27 PM

@RajorshiKoyal If a government or central bank can issue money without an asset backing it, then it's possible to get runaway inflation when people lose trust in that central bank. Eg, en.wikipedia.org/wiki/Hyperinflation_in_Zimbabwe

Got you...

Diamonds are expensive because people agree they are expensive, and De Beers encourages everyone to maintain that belief. ;)

ok..got the thing...

Why is extreme volatility makes it so ideal speculation for gambling?

In the modern era, platinum group metals are expensive. But in the first century or so of European colonisation of South America, platinum was considered to be an unwanted contaminant found in various South American gold mines. Sometimes, it was just tossed on the ground as scrap.

Then some crafty people realised they could mix it with gold. That eventually caused serious problems, with a lot of gold coins being found to be contaminated with platinum. The war against the use of platinum in forgery lasted over a century. The problem was only solved when platinum became valuable in its own right. It has some useful properties: it has a high melting point, and is very resistant to acids and other chemicals.

@RajorshiKoyal I think you've got that bacwards. (But I am not an economist, or a cryptocurrency expert). If a currency is highly volatile then it's very sensitive to the effects of speculation & other forms of gambling.

But why volatile..

I still could not figure it out..

I mean voltaile has to do with low melting point

What is the analogy?

2:43 PM

Conversely, if a currency is highly volatile, then speculative investment carries a higher risk. Your potential profits can be higher, but so are your potential losses. What's the benefit of winning a million dollars if tomorrow those dollars lose 90% of their value?

Volatility (finance)

In finance, volatility (usually denoted by σ) is the degree of variation of a trading price series over time, usually measured by the standard deviation of logarithmic returns. Historic volatility measures a time series of past market prices. Implied volatility looks forward in time, being derived from the market price of a market-traded derivative (in particular, an option). == Volatility terminology == Volatility as described here refers to the actual volatility, more specifically: actual current volatility of a financial instrument for a specified period (for example 30 days or 90 days), based...

Got you..I can so well relate to how a volatile currency would be a good gamble

mine a cryptocurrency what does this mean?

@RajorshiKoyal It's complicated. ;) It's an important part of how the blockchain works. It involves doing huge amounts of computations on a very fast computer. See en.wikipedia.org/wiki/Proof_of_work

"There is no act to regulate cryptocurrency in India."

What does this mean?

What is meant really by Presidency in the context

I come across Presidency University..

Presidency bank..

Why are they called so..

3:06 PM

@RajorshiKoyal This article might be helpful: en.bitcoin.it/wiki/Mining You probably need to browse that wiki and various other cryptocurrency FAQs for a few days before it all starts making sense.

@RajorshiKoyal It means that India currently has no laws that cover the uses of cryptocurrency.

Anyway, I think it's time to wrap up this discussion of cryptocurrency. I didn't intend to start a discussion, I just wanted to mention the insane amount of energy that Bitcoin mining consumes.

ok..

Why do you always put two periods at the end? It looks strange.

ok.Sorry.

Can you assist me with the presidency question that I posted?

3:28 PM

@ACuriousMind In Devanagari, a | marks the end of a sentence and || marks the end of a verse or paragraph. See en.wikipedia.org/wiki/Devanagari#Punctuation

Interesting

It's a fun (and pretty) writing system. The rules for combining consonants are fairly regular, so a beginner may not know how to write an uncommon consonant cluster, but it's usually pretty easy to figure out an unusual cluster when you read it. IOW, it can be easier to read Devanagari than to write it. ;) I studied it for a while a few decades ago, but I'm badly out of practice, and I've forgotten most of what I learned. :(

FWIW, there are 10 verb conjugation classes in Sanskrit, and no irregular verbs. The irregular verbs in more modern Indo-European languages are mostly artifacts of the ancestral verb classes in proto-Indo-European.

3:48 PM

What is by presidency bank?Why is the word presidency being used?

@RajorshiKoyal you don't need to repost the same question - if someone here right now knew the answer and wanted to answer, they would've seen your question already.

Alright:_0

:-)

@RajorshiKoyal See here. You really should try to use Google (or some other search engine) before asking such questions. Otherwise, you will needlessly annoy people in the various chat rooms you visit...

ok..

4:07 PM

I tried google but could not get it @PM2Ring

Why presidency?

In our country we have Presidency University also..

4:36 PM

@PM2Ring cool! why/how did you study devnagari?

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